Note: Descriptions are shown in the official language in which they were submitted.
11;)79~
The present invention relates to the manufacture
of metallic containers such as cans.
A significant proportion of foods and beverages,
particularly soft drinks and beer are at present packaged in
metal cans.
Three-piece cans are made by fabricating a tubular
side wall, securing a disk-shaped bottom at one end of the
body, filling the can, and securing a di~k~shaped lid at the
opposite end of the body.
` Two-piece cans are usually made by deforming a
disk-shaped blank into a can body (a tubular sidewall having
an integral, disk~shaped bottom at one end), filling the can
and securing a disk-shaped lid at the opposite end of the
body. The wall of a two-piece can is thinned during forma-
tion while the bottom remains ~ubstantially the same thick-
ness as the blank from which the can is made. (Terminology
used in the industry has not always been unambiguous. Oc-
casionally, two-piece cans are termed "one-piece" cans or
"seamless" cans, because their can bodies are all one seam-
less piece. For purposes of this application, two-piece can
and three-piece can terminology will be utilized.)
At first, th~ee-piece cans were easier to make in
desired sizes and were predominant, however, the apparent
attainability of the goal of making more, adequately strong
cans, more efficiently encouraged the development of two-
piece can technology. As one result, much of the soft drinks
and beer is presently being canned in two-piece cans manu-
factured by drawing and ironing or drawing and redrawing thin
sheet disks of aluminum or steel. The industry is constantly
motivated to devise innovative means to manufacture newly
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conceived can body and end structures to reduce the raw
materials consumed in can manufacture. Since the yearly
consumption of cans for beer and beveragesis substantial
any saving in metal consumption is readily translated into
a substantial monetary savings.
For whatever reason, the bottoms of cans are pres- ~
ently either substantially flat, or are centrally domed ;
inwards and provided with a perimetrical ring upon which
the can stands when supported on a flat surface.
Can bodies are designed to withstand certain pres-
sures. Traditionally, beer cans are designed to withstand
up to 90 p.s.i. while the actual pressure may be substan-
tially less in application. Nevertheless, the cans so
fail; the primary source of failure is the bottom of the
can. Failure occurs in the form of reversal, a term used
to indicate that the inwardly or upwardly domed portion of
the can body is distorted to bulge outwardly to cause the
can bottom to be uneven.
- It is accordingly an objective of the present inven-
tion to provide a stronger can bottom configuration than
heretofore attainable with conventional bottom configura-
tions.
The present invention provides a metallic can body
with a tubular sidewall extending upwards from a bottom end
wall, the bottom end wall being provided with two coaxial,
radially spaced annular contact bands, the first of these
being radially outermost and initially solely effective ~'
for supporting the can body upright, and the second of
these comprising a plurality of spaced feet, said feet
becoming solely effective upon sufficient internal pres-
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surization of the can body as to lower the second annularcontact band below the first.
The present invention further provides a canning
operation in which can bodies are being filled with a
beverage or the like, closed, and subjected to a further
processing step such as pasturization in which pressure
within the cans is raised to within a preselected range
and each can is tested to determine whether each can has
become sufficiently internally pressurized during said
further processing step, further comprising the steps of: .
(a) selecting a metallic can body with a tubular sidewall
extending upwards from a bottom end wall, the bottom end
wall being provided with two coaxial, radially spaced
annular contact bands, the first of these being radially
outermost and initially solely effective for supporting
the can body upright, and the second of these con~prising a
plurality of spaced feet, the feet becoming solely effec-
tive upon sufficient internal pressurization of the can
body as to lower the second annular contact band below
the first; and (b) upon conclusion of said further pro-
cessing step, sensing, with respect to each can, whether
it stands at a height that corresponds to its being sup-
ported upon said second annular contact band thereof or at
a lesser height that evidences a failure to achieve suffi-
cient internal pressurization.
The container is typically a drawn and ironedbeverage can body whose bottom wall is coaxially formed
with
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a ring of individual outwardly convex dimples or feet.
Otherwise, the can bottom wall may be flat, centrally domed
outward or inward, provided that after canning i8 completed,
of all the can bottom portions the feet protrude furthest
outwards to provide a stable support for the can. The bot-
tom design disclosed herein may be used on two or three-piece
beer and beverage containers, aerosol container~, and other
similar pressure restraining containers. ~n the preferred
embodiment, the bottom is intially domed inwards and a ring
at the outer perimeter of the can ~ottom protrudes furthest
outwards. Then, after filling and closing, as the can con-
tents are internally pressurized, e.g. during beer pasteuri-
zation, the central dome pops outwards projecting the feet
outwards beyond the perimetrical ring. The can bottom with
feet thereon produces a stronger can if the usual thickness
of can stock is used, and can be acceptably strong yet stable
if, instead, a thinner can stock is used.
The principles of the invention will be further
discussed with reference to the drawing wherein preferred
embodiments are shown. The specifics illustrated in the
drawing are intended to exemplify, rather than limit, aspects
of the invention as defined in the claims.
Figure 1 is a fragmentary longitudinal sestional
view of a conventional two-piece, flat-bottom can body, with-
out internal pressurization;
Figure 2 is a fragmentary longitudinal sectional
view of the conventional can of Figure 1, after internal
pressurization of a sufficient magnitude to cause the can
bottom to centrally dome outward, creating a rocker;
Figure 3 is a fragmentary longitudinal sectional
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view of a conventional two-piece, inwardly domed bottom can
body, without internal pressurization;
Figure 4 is a bottom plan view thereof;
Figure 5 is a fragmentary longitudinal sectional
view of the conventional can of Figures 3 and 4, after inter-
nal pressurization of a sufficient magnitude to cause the
dome to revert or dome outwardly to produce a distorted
rocker-shaped can bottom;
Figures 6and 7 are fragmentary longitudinal sec-
tional views of a first embodiment of the can of the inven-
tion respectively before and after internal pressurization.
~he remainder of the can above the view may be conventional
in structure and appearance~
Figures 8 and 9 are fragmentary longitudinal ~ec-
tional views of a second embodiment of the can of the inven-
tion respecitvely before and after internal pressurization.
The remainder of the can above the view may be conventional
in structure and appearance.
Figure 10 is a longitudinal sectional view of a
third and presently preferred embodiment of a can of the
present invention, shown filled and closed, but not internal- ~-
ly pressurized, so that the feet remain retracted.
Figure 11 is a bottom plan view thereof; and
Figure 12 is a longitudinal sectional view of the -
can of Figures 10 and 11, following a time when internal
pressurization thereof has everted the dome and thereby ex-
tended the feet.
Some present can bodies 10 (Figure 1) have a sub-
stantially flat bottom 12, which serves adequately if the
metallic material of which the can body 10 is formed has
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such a combination of thickness and stiffness that internal
pressure, for instance resul~ing from gas in the canned pro-
duct, after the can is filled and closed, domes the can end
12 outwards (Figure 2). Such a distension of the can bottom
gives the can an unstable base; it becomes a "rocker" which
will not stand stably upright on a flat surface S.
Other present can bodies 14 (Figures 3 and 4) in-
itially have a centrally inwardly domed bo'_tom 1~, surrounded
by a perimetrically continuous, axially outwardly convex ring
18 where the bottom 16 joins the can sidewall 20. Normally,
the ring 18 provides an extensively distributed annular con-
tact band in a flat, radiating plane, so that the can will
stand stably upright. However, if the metallic material of
which the can body 14 is formed has an insufficient strength,
or if the internal pressure in the can, once it is filled
and closed, becomes too great, the can bottom 16 will evert
and the can bottom will become misshapened to thus produce
an unstable can. If the eversion does not place the center
24 of the dome axially further out than the contact band 22,
the can will continue to have the capability of standing
stably upright on a flat surface S. Clearly, a certain mag-
nitude of growth upon eversion will place the center 24 axi-
ally beyond the contact band 22 (Figure 5) whereupon this
can also becomes a "rocker", unable to stand stably upr-ght.
Apparently, a smooth can bottom central region
that is surrounded by an unbroken, ring-shaped structure is
predispsoed to evert or dome outwards. We have found that
this propensity is substantially reduced if the smoothness
of the border of the central region of the can bottom is
broken-up impressing a plurality of localized dimples or
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feet therein. By "localized", it is meant that, while the
feet may be arranged in a coaxial ring on the can bottom,
the feet are a plurality of individuals which are spaced-
apart from one another angularly of the can longitudinal
axis.
One version of the new can bottom is shown in
Figures 6 and 7, a second version is shown in Figures 8 and
9, and a third, presently preferred version, is shown in
Figures 10-12.
The can body 30 shown in Figure 6 is just like the
one shown in Figure 1, except that the can flat bottom wall
32 has been locally deformed at, for instance, five equi-
angularly spaced sites to provide a plurality of axially
outwardly projecting individual dimples or feet 34, located
intermediate the center 36 and perimeter 38 of the bottom 32.
For instance, the feet may be of circular figure and gener-
ally part-spherical profile. Other shapes, such as ovals,
tear drops, toroids and generally triangular, rounded-apex
star points could be used.
It has been discovered that the exact dimensions,
locations, or numbers of the dimples may be critical in that
fracture or rupture may occur if certain depth to diameter
ratios of the dimples or the ultimate strength of the mate-
rial, are exceeded. Otherwise, the present invention in-
cludes various arrangements of plural dimples on can bottoms.
Example I
Fourteen drawn and ironed two-piece beverage can
bodies 30 manufactured ~rom 16.5 thousandths of an inch
thick 3004-Hl9 aluminum alloy to meet United States Brewers
Association, Inc. standards for a 211 by 413 can body were
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each impressed with five feet 34, using an internal die with
five one-half inch diameter part-spherical foot-formers pro-
jecting axially outwards approximately 0.125 inch at their
respective centers. A range of pressing forces used among
the several cans caused feet of a progression of magnitudes
of center depths to be formed. Externally, each can bottom
was backed with a die having formed reliefs which matched
the internal foot-formers. Five of the fourteen test cans
were not tested. On the nine tested, foot-forming die pres-
sure ranged between 3500 pounds and 6000 pounds, with an
average of 4000 pounds. Individual foot center depths ranged
from 0.102 inch on one relatively lightly impressed can, to
0.110 on several cans impressed using at least 4000 pounds.
Each of the nine cans was internally pressurized to 160
pounds per square inch with no indications of metal failures
or leaks.
(Usually, beverage cans are not called upon to
contain an internal pressure of more than about 100 p.s.i.,
e.g. when used to contain carbonated soft drinks.)
In addition, the nine cans were tested for support
stability by standing each upon a flat surface S (Figure 7)
and increasing the internal pressure therein until the can
bottom centrally domed outwards enough to cause the center
; 36 t~ touch the surface S. That condition was reached at
an internal pressurization of from 140 to 155 p.s.i., in
proportion to foot depth, at an average of 148 p.s.i. Again,
this is a substantially greater internal pressurization than
normally present in carbonated beverage cans.
It has been determined, that the cans of this ex-
ample, when internally pressurized in the ranges tested
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'igrow" from about 80 to about 100 thousandths of an inch
taller, as a result of centrally outward doming of the can
bottom. While that magnitucle of growth, and an attendant
increase in can volume is deemed acceptable for a significant
segment of the can market, there are some instances where it
would be undesirable and that has led to the development of
the embodiment shown in Figures 8 and 9.
The can 40 shown in Figures 8 and 9 is identical
to the can 30 of Figures 6 and 7, except that in the second
embodiment 40, the can bottom wall is even initially gener-
ally spherically domed slightly outwards over its full radial
exten by, for instance, sixty to seventy thousandths of an
inch or so. Accordingly, when the can 40 is filled, closed
and internally pressurized to about lO0 p.s.i., it will
}5 "grow" only about 20 to 30 thousandths of an inch taller.
That is because the initial doming partially "pre-grows" the
can. The can 40 can be made of the same thickness of metal
sheet as is presently used to make beverage cans which are
similar but for lacking feet, e.g. 16.5 thousandths inch
thick sheet. In that case, the can 40 will be st~ronger, and,
for instance, able to contain about 148 pounds per square
inch internal pressure yet remain stably supported on its
feet 44 without its center 46 engaging the support surface
S. That compares with about 90-lO0 p.s.i. internal pressure
for over-doming protrusion or eversion of an otherwise sim-
ilar, conventional domed-bottom but non-footed can.
A can 40 which has a bottom strength more nearly
equivalent to conventional domed-bottom cans can be made of
thinner sheet, for instance of 13.5 thousandths inch thick
3004-Hl9 aluminum alloy can stock. That results in a saving
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of from about 11 percent up to a maximum of 18 percent in -
can body metal weight. Such a saving in metal weight is
estimated to result in a sa~tings of $2.00 per l,G00 cans or
$90 million per year for the United States beer and beverage
industry.
Note that even before the can 30 of Figures 6 and
7 or can 40 of Figures 8 and 9 is internally pressurized,
the feet protrude axially outwards further than the peri-
metrically extending ridge where the can body bottom meets
the body sidewall. Although there are ma~y instanceq where
that will cause no problem, some can makers and canners who
would be natural customers for the present invention may have
a reason for concern that the protruding feet would cause
jamming or erratic conveying on the particular designs of
conveyors those can makers or canners have in use at their
existing plants.
Also, one must consider the axial compressive stres4
placed on cans when they are being double-seamed at the can-
ners. A beverage can may be subjected to as much as 360
pounds axial compressi~e force (typically 250) during filling
and double-seaming. Especially where lighter than presently ;
conventional gauge sheet is being used, the feet of the cans
of Figures 6-9 could be flattened or crushed somewhat, caus-
ing too many rejects.
With a view toward anticipating and overcoming the
difficulties set forth in the two foregoing paragraphs, for
~ ances where the prospect of either being a problem is a
wQ~risom~ ~dtcr~, ~he present inventors developed their third
embodiment, the ane shown in Figures 10-12.
Figures 10-12 bear comparison with Figu~2æ 3-5,
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1~79659
which depict the corresponding conventional can.
In the embodiment 50 of Figures 10-12, the body i8
formed as described above with respect to Figure 3, except
that the bottom 52 is provided with a plurality of feet 54
as described above with respect to Figure 6. The radius of
the imaginary coaxial circle on which the feet 54 are pro-
vided, compared to the magnitude of initial outward concavity
of the bottom 52 (Figure 10) and the like center depths of
the individual feet 54 is such that, initially, the can bot
tom 50 rests on the annular perimetrical rim or band 56 where
the bottom 52 joins the sidewall 58. This is important. It
means that while such a can is being conveyed at the can
making plant, and at the brewers or other cannery, its feet
are retracted and not available to foul in conveyors. Ac-
cordingly, the can bottom formed as disclosed herein may be
used on conventional filling lines without special modifica-
tions. Note from Figure 10 that the feet 54 do not extend
down to the flat support surface S. It also means that when
the can i8 being filled, e.g. with carbonated beverage 60
and being provided with a lid 62, perimetrically seamed
thereto at 64 at the opposite end of the can body, the can
will have widely distributed, extensive support at 56, which
is much like the way and place that conventional cans are
supported. See Figure 3.
However, after the cans S0 have been closed and
are subjected to internal pressurization, for instance during
a conventional canned beer pasteurization step, the initially
concave inward (Figure 10) can bottom 52 everts and becomes
convex outwards (Figure 12). That excursion which may typi-
cally occur at 18-20 p.s.i., causes the feet 54 to extend
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10796~9
axially outward further than the band 56, so that the in-
ternally pressurized can 50 stably stands via its several
feet 54 upon the flat surface S. In this embodiment, the
feet may be axially shorter, for instance 80-85 thousandths
of an inch in depth, and the can may "grow" as much as about
160 to about 180 thousandths of an inch in height when trans~
forming from its Figure 10 shape to its Figure 12 shape.
Such a gain in height is accompanied by a change in volume
that also depends upon the length to diameter ratio of the
can. ~ typical increase in contained volume for a can 50
drawn and ironed using equipment normally used to make a 12-
ounce, 211 beverage can, i.e., a can having a diameter of
2-11/16 i!~lch, is from about 13.8 ounces to about 14.35 ounces.
These footed cans 50, when made from 13.5 thousandths of an
inch thick 3004-Hl9 aluminum alloy can stock, will withstand
being internally pressurized up to at least 100 p.s.i.,
without becoming unstable due to over-doming.
It should be apparent that the principles of the
invention will apply equally well no matter what contents
2~ internally pressurize the can. The invention is thus not
limited to beer, soft-drink or beverage cans and may find
application for aerosol cans as well as other pressurized
containers. hikewise, the present invention may be employed
in the formation of a three-piece can body to provide similar
results.
While a particular alloy in widespread use has
been cited in the examples, it is not limiting. The present
invention may find equal acceptance in the manufacture of
tin-plated steel cans as well as aluminum cans. The inher-
ent advantage of the present invention is not dependent upon
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the material of which the can is manufactured.
A can bottom according to the present invention
may be formed in a separate pressing step, or by appropriate
bodymaker tooling modificaitons to include foot-formers to
form the feet simultaneously with the can body bottom. Al-
ternatively, the feet may be formed in the cup prior to its
receipt by the body-maker or as a separate step at the con-
clusion of the body-maker stroke. Other means or methods
for manufacture of the present invention will occur to those
skilled in the art.
One embodiment of the present invention may be
utilized to advantage in monitoring or indicating that pre-
determined internal pressures have been achieved. The pres-
sures may indicate that the contents of the can has gone
through certain predetermined heat or pressure ranges to
thus indicate pasteurization, pressure utilization or pro-
cessing in the form of cooking, blanching or sterilizing.
In a traditional canning operation of carbonated
drinks, the can is supplied with a predetermined amount of
liquid, the liquid and any resulting foam is permitted to
settle and then the can is closed. The head space above the
liquid is occupied, traditionally, by carbon dioxide prior
to closure. In most beer canning processes, the beer is
pastuerized after it is enclosed in the container, Pres-
surization of the container^also results after the containeris closed.
In the embodiment of the present invention where
the bottom is concave inwardly prior to pressurization, the
volume of the container after pressurization is greater than
the volume of the container prior to pressurization. Thus,
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the actual head space provided at the mouth of the can body
could possibly be reduced knowing that the volume of the can
would actually increase after closure. Such reduction in
head space may in reality depend upon improved methods of
transporting the container after filling and prior to closure
or other modifications or improvements of the canning process.
Nevertheless, to further reduce the amount of metal
used to manufacture a can and to optimize one use of the
present invention, the dimensions of the can body may be
modified to selectively provid.e the desired can volume after
closure and pressurization.
Modification of can body dimensions could occur
in various ways. For example, the length of the body could
be varied. Alternatively, the diameter of the body could be
decreased or a combination of changes in length and diameter
could be selected. The particular change envisioned may de-
pend upon customer desire or the desire of the filler not
to modify certain structural components of his filling line.
The ultimate result in any case would be a further reduction
in metal needed to provide a can of a desired volume. In-
herent in meeting this objective is the novel structure dis-
closed herein providing a can body which actually "grows"
after closure due to internal pressurization.
Because the integrally footed container can be
modified to some extent without departing from the principles
of the invention as they have been outlined and explained in
this specification, the present invention should be under-
stood as encompassing all such modifications as are within
the spirit and scope of the following claims.
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